1. Field of Invention
The invention generally relates to methods and apparatuses for investigating bio-molecules, and specifically relates to methods and apparatuses for determining the sequence of a nucleic acid.
2. Prior Art
The quest for low-cost methods of sequencing nucleic acids has been driven by its recognized importance to biological and medical research, and ultimately by its potential to impact the practice of medicine. Consequently, many techniques have been explored and reviewed, including variations on the classic chain-termination strategy of Sanger et al. PNAS 74:5463 5467 (1977), pyrosequencing, see for example Hyman E. D. Analytical Biochem 174:423 436 (1988), and other sequencing by synthesis or sequencing by incorporation methods, see for example Ronaghi et al. Science 281:363 365 (1998), sequencing by hybridization techniques, for example Strezoska et al. PNAS 88:10089 10093 (1991), including micro-array techniques, for example Chee et al., Science 274:610 614 (1996), and direct imaging of bases by micro-probes, for example Hansma et al. Science 256:1180 1184 (1992). A hybrid sequencing by hybridization and chain-termination technique is presented by Head et al. in U.S. Pat. No. 6,322,968 that employs probes having a short spacer arm. In their method, probes are lengthened by the polymerase and a chain-terminating and labeled nucleotide. The method is an array technique with the added complexity of an enzymatic process. In general, all these sequencing methods suffer from one or more of the following issues: short read lengths on un-correlated fragments, time-consuming cyclic processes conducted in expensive equipment, excessive consumption of expensive reagents, difficult and costly to analyze data sets, and reliance on alternate means for generating a sequence scaffold or map. The present invention is designed to circumvent these issues.